The invention relates to a prefabricated underlay material for location between the upper surface of a load-bearing floor and a parquet or other continuous surface material, which underlay material comprises a substantially flexible sheet material and dampening projections formed of porous resilient material on at least one surface of the sheet material, distributed along said surface of the sheet material and having a total projection area less than the area of the sheet material. The invention also relates to a method for the manufacture of an underlay material for location under parquet or other continuous surface material, in which method dampening projections formed of porous resilient material are arranged located at intervals on at least one surface of an substantially flexible sheet material, the total projection area of said dampening projections being less than the area of the sheet material.
The principal function of the underlay material is to act as an installation base for parquet, floorboards, laminated wood panels, plywood or other relatively hard surface material between the surface material and the load-bearing floor material. The load-bearing floor has an upper surface corresponding at least to the installation area of the parquet or equivalent surface material and the underlay is located on this upper surface in connection with the installation work before putting the parquet or equivalent surface material in place. The material of the load-bearing floor is typically concrete, although other materials sometimes occur too, and the underlay material should then even out minor irregularities in the upper surface of the concrete. In addition the underlay material should act as acoustic insulation and dampen noise, which is created inter alia when walking on a relatively hard surface. Besides this the underlay material should act as a ventilating layer under the parquet and enable the escape of possible moisture from the load-bearing floor material, such as from a concrete slab. This is especially important in new building, because due to tight building timetables drying out of the structures has generally remained partially deficient. Further, moisture must not be allowed to migrate from the load-bearing floor material, such as a concrete slab, to the surface material, such as parquet, because then there would be a risk of damp damage to the parquet, causing inter alia deformation of the parquet.
One prior known solution for use as an underlay material for parquet is a uniform layer of porous polyethylene approx. 1-3 mm thick. The solution provides good acoustic insulation, a good installation base for the parquet and the underlay is easy to install, but the surface of the load-bearing concrete slab is then covered by an airtight layer, which prevents the escape of moisture from the slab. The solution based on balls of expanded polystyrene located between polyethylene films likewise provides poor escape of moisture. Such a solution is described in utility model DE-G 91 15 773, although there an attempt has been made to alleviate the problem by making one of the polyethylene films perforated. Earlier corrugated cardboard was commonly used as an underlay material, but in time becomes crushed and loses its elasticity. Further, moisture can migrate directly to the parquet through the layer of corrugated cardboard and damp corrugated cardboard promotes the growth of mould, which is a health risk for users of the accommodation. Further known for use as an underlay material is cardboard, on the surface of which are pieces of cork attached by bituminous adhesive, or according to Patent Application FI-956192 felt, to which are attached with the aid of a bituminous layer impact noise dampening plastic beads, which are embedded in the bituminous layer. Both these underlay materials, however, easily dirty the accommodation during the installation phase. If the black bitumen layer contacts a light-coloured wall it leaves marks, which are difficult to remove. Further, pieces of cork become completely or partially detached from the bituminous adhesive, forming debris.
An attempt to solve these problems has been made in the underlay material described in patent publication FI-86996, which consists of a supporting band of paper or cardboard on one side of which pre-expanded polymer granules are fixed with the aid of a polymer coating. This underlay material is manufactured by pressing a web of paper or cardboard and molten plastics extruded from a nozzle together in the nip between a press roll and a cooling roll at the same time as pre-expanded, i.e. porous, plastic granules are introduced into said pressure nip by feeding them onto the top of the chill roll. The porous plastic granules are thus carried on the surface of the chill roll into the nip between the rolls, where they are pressed into the still molten polymer coating layer, as can be seen from the figures in the publication. In the publication LD polyethylene is used as the coating polymer and pre-expanded polystyrene granules are used as the porous plastic granules. In the compression test reported the deformation was 33% at a load of 2.0 kp/cm2 (=196 kPa) and compression time of 10 minutes, which seems a high value. As an end product the underlay material according to the publication would in principal function in the intended fashion, but the manufacturing technique is very problematic, so that useable underlay material is not obtained on the necessary production scale. The product described in the publication is thus merely theoretical, and not applicable in practice. It has not been brought to the market at all.
The solutions used earlier have each been individually useable to some extent in respect of some certain property, but none of the known underlay materials has succeeded in combining all the required good properties and eliminating all the drawbacks at the same time as being possible to manufacture efficiently and economically. The invention aims to combine in the same solution all the good properties of an underlay material and to eliminate the drawbacks present in earlier solutions. In this connection it should also be noted that the properties of a good underlay material include a certain yielding under load with return to its former state upon removal of the load, so the manufacturing technique for the underlay material should be such that a material satisfying the requirements can be used as the resilient material. The finished underlay material should also be easy to handle and install, non-messy and durable. Further, an aim of the invention is such underlay material which would be easily manufactured also in large quantities and with very small material waste and for which the production apparatus would be simple and not require large investments. For the components of the underlay material it should be possible to use economically advantageous materials. All in all, the underlay material should be got competitive in price compared to known underlay materials. If necessary it should be possible to incorporate a moisture barrier in the underlay material or to omit it.